The quick summary of how it works is: You buddy 2 credits to game host, you are assigned a game buddy, you get two books for your game buddy off their wish list, they get two books for you off your wish list for you, when your books are received by your buddy you get your 2 credits back.

End of game, you have two wishlisted books you can now remove from your wishlist without spending credits, and you've made some new friends!